Facebook CEO Mark Zuckerberg and his wife, Dr. Priscilla Chan, on Monday announced the birth of their second daughter, August, with a letter about childhood to the newborn.

“The world can be a serious place. That’s why it’s important to make time to go outside and play,” the couple wrote in a letter posted on Facebook. “You will be busy when you’re older, so I hope you take time to smell all the flowers and put all the leaves you want in your bucket now.”

When the couple celebrated the birth of their first daughter Max in 2015, they also publicly shared a letter in which they pledged to donate 99 percent of their Facebook stock to fund philanthropic efforts.

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They formed the Chan Zuckerberg Initiative to “advance human potential and promote equality for all children,” focusing on education, curing diseases and other efforts. At the time, the gift was worth about $45 billion, one of the largest in the nation’s history.

While the organization’s mission is a challenging feat, the couple told their daughter in a letter that they’re optimistic about her generation and the future.

The name August is a form of the name Augustus, which means revered or someone held in high regard, according to parenting site Baby Center.

The couple has also shared some of the struggles that have come with pregnancy in the past. Chan had three miscarriages before giving birth to their first child.

Zuckerberg will be taking some time off now that his second daughter was born. The tech mogul said last week that he plans to take two months of paternity leave like he did when his first daughter was born.

But the couple didn’t spend too much time dwelling on adulthood in the letter to their second daughter. They talked about joys of childhood, telling August that they hope she reads a lot of Dr. Seuss books, rides the carousel, runs laps around the living room and takes a lot of great naps.

“Childhood is magical. You only get to be a child once, so don’t spend it worrying too much about the future,” the couple wrote. “You’ve got us for that, and we’ll do everything we possibly can to make sure the world is a better place for you and all children in your generation.”

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